Conventional 802.11 wireless receivers typically include, among other units, a radio frequency unit (RFU), an analog baseband processing (ABB) unit, a digital baseband processing (DBB) unit, and a media access control (MAC) unit. Such conventional 802.11 wireless receivers typically receive and decode all frames detected by the wireless receivers. For example, after being decoded, frames intended for a host are provided to the host, while frames not intended for the host are discarded or ignored. Unfortunately, receiving and decoding frames that are not intended for a host wastes power.
A classification/filtering scheme is generally used to determined whether or not frames are intended for a host. Classification is a process of extracting information from the MAC Header and signal field of an incoming frame—e.g., a MAC address of the receiver (target address), a MAC address of the sender, a frame type, a subtype, and QOS—and assessing the information with a set of policies as defined by a host, which results in classification of the frame as being intended or not intended (filtered) for the host.
Information required for classification of a frame is typically available in a relatively small portion at the beginning of the frame, thus providing ample opportunity to save power by switching the receiver subsystems to low power states for the remaining duration of a frame determined to be filtered out.
Conventionally, if a filtered frame is received correctly (e.g., frame check sequence (FCS) pass, cyclic redundancy check (CRC) pass), then the duration-id field in the incoming frame is used as a virtual carrier sense, and network allocation vector (NAV) processing is triggered for the end of frame processing associated with a carrier sense multiple access with collision avoidance (CSMA/CA) protocol. Additionally, if a filtered frame is received incorrectly (e.g., FCS fail, CRC fail), then extended inter-frame spacing (EIFS) is triggered for the end of frame processing for the CSMA/CA protocol.